In this description, the term "cement" is used to designate silicate cement compositions such as Portland cement, pozzolan cements, hydraulic limes and natural cements.
In whatever form it is used--tempered cement, mortar or concrete--a good mixture based on hydraulic cement as the binder should give entirely satisfactory results from the triple viewpoint of preservation, mechanical resistance and economy. It is well known that if the conditions of preservation and resistance are to be met satisfactorily, independently of the economic factor, the use of a minimal amount of water required to make the mixture in the useful period when it can be worked, is of vital importance. To reduce the proportion of this mixture water, suitable agents called "thinners" or "water reducers", making it possible to work with less water, are ordinarily used in preparing mortar and concrete.
It can be assumed that the mechanism that makes it possible to reduce the proportion of water necessary by use of water reducing agents is such that the resulting water-reducing effect is produced synergistically by one of the two following modes of operation: by the first mode, a cement dispersion is created which homogeneously distributes the cement particles themselves and increases the fluidity of the resulting tempered cement, thereby making the dispersion suitable for adequate working with a smaller amount of water than would others otherwise be used. According to the second mode, an air-entraining agent produces very fine separate air bubbles in the mortar, concrete, etc. which air bubbles increase the fluidity of the cement mixture acting like ball bearings, which allows a corresponding reduction of the amount of water required.
Consequently, many water reducing agents used in practice are made up of a cement dispersion agent and an air-entraining agent, and their effects as such depend in great part on the latter constituent.
However, this effect of reducing the amount of water necessary, imparted by an air-entraining agent, is determined by the amount of air that must be entrained by this agent, and it is evident that the effect is increased if a greater amount of air is entrained. An increase in the quantity of air entrainment, on the other hand, is accompanied by a corresponding reduction of the resistance of the hydraulic cement and, for this reason, the amount of air that can be entrained in the concrete or a similar binder and, correlatively, the effect of reducing the amount of water necessary that can be obtained with an air-entraining agent, are limited. If it is desired to obtain an improved effect in this reduction of the amount of water without a corresponding reduction in strength, it is quite essential to find a better dispersion agent for the cement particles.
The effectiveness, as cement particle dispersion agents, of the salts of high molecular weight condensation products of naphthalenesulfonic acid formaldehyde is well known (of Japanese Pat. No. 485,391 and German Pat. No. 1,238,831). Other prior art of interest are U.S. Pat. No. 3,053,673; Belgian Pat. No. 847,038 (French equivalent No. 2,367,028); French Pat. Nos. 1,305,098; and French 1,415,646.